A typical cellular communication system includes one or more base stations (BS) and multiple mobile stations (MS), as shown in FIG. 1A. Each BS defines a cell of coverage where each MS can communicate with a BS via a BS-MS link while within communication range of the BS cell coverage. In many cellular systems, radio resource management (RRM) for orthogonal frequency division multiple access (OFDMA)-based cellular systems is utilized. Such systems address resource (frequency/time/power) allocations among BS-MS links (i.e., transmission channels defined by frequency carriers, spreading codes or time slots). There are two types of RRMs: intra-cell RRM and inter-cell RRM. The intra-cell RRM tries to assign resources to MSs or BS-MS links within a cell (and prevent interference among MSs). The inter-cell RRM tries to assign resources to multiple cells (and prevent interference among BSs and MSs in different cells). Available frequency bandwidth is divided into frequency subcarriers and assigned to the BS-MS links based on channel conditions and traffic demands. End-to-end throughput between a BS and MS is a function of Single Interference Noise Ratio (SINR) of the link between the BS and MS.
Intermediate relay stations (RS) have been used for improving throughput, coverage and spectrum efficiency of cellular systems. FIG. 1B shows an example cellular system including a base station BS, multiple mobile stations (MS) and relay stations (RS1, . . . , RS6), wherein different relay cells are allocated different frequency resources. A two-hop transmission takes place between a BS and MS via a RS, wherein an RS may be an MS itself. The introduction of relay stations brings forth new challenges to the RRM design. RRM for relay enhanced cellular (REC) systems has to address resource allocations among BS-MS, BS-RS and RS-MS communication links.
In order to support relay stations, communication time frames can be divided into access zones and relay zones. In access zones, relay stations communicate with two-hop mobile stations. In relay zones, relay stations communicate with the BS. The BS can communicate with direct mobile stations (or one-hop mobile stations) in both access zones and relay zones. Note that access zones and relay zones are defined in time domain.
Conventional RRM algorithms for REC systems jointly consider multiuser diversity and link balancing to maximize overall system throughput. Such RRM approaches attempt to maximize the overall system throughput by assigning subcarriers to relay station and mobile stations with good channel conditions. Relay stations and mobile stations with bad channel conditions may not be assigned sufficient resources to meet their minimum data rate requirements.